Aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid or their di-esters, dimethyl terephthalate as for example, are used to produce a variety of polyester products, important examples of which are poly(ethylene terephthalate) and its copolymers. The aromatic dicarboxylic acids are synthesized by the catalytic oxidation of the corresponding dialkyl aromatic compounds which are obtained from fossil fuels such as those disclosed in US 2006/0205977 A1. Esterification of these diacids using excess alcohol produces the corresponding di-esters has been disclosed in US2010/0210867A1. There is a growing interest in the use of renewable resources as feed stocks for the chemical industries mainly due to the progressive reduction of fossil reserves and their related environmental impacts.
Furan-2,5-dicarboxylic acid (“FDCA”) is a versatile intermediate considered as a promising closest biobased alternative to terephthalic acid and isophthalic acid. Like aromatic diacids, FDCA can be condensed with diols such as ethylene glycol to make polyester resins similar to polyethylene terephthalate (PET) as disclosed in Gandini, A.; Silvestre, A. J; Neto, C. P.; Sousa, A. F.; Gomes, M. J. Poly. Sci. A 2009, 47, 295. FDCA has been prepared by oxidation of 5-(hydroxymethyl) furfural (5-HMF) under air using homogenous catalysts as disclosed in US2003/0055271 A1 and in Partenheimer, W.; Grushin, V. V. Adv. Synth. Catal. 2001, 343, 102-111.
There is a need for a technique for the production, purification, and isolation of esterification products of FDCA and alcohols to make higher purity or higher yield of dialkyl furan dicarboxylates without the necessity for downstream separation of large volumes of high boiling compound intermediates such as 5-(alkoxycarbonyl)furan-2-carboxylic acid.